The presently disclosed subject matter relates to an electrical impedance measuring apparatus which is called the EIT (Electrical Impedance Tomography) or the like.
In artificial ventilation therapy of respiratory disease such as ARDS (Acute Respiratory Distress Syndrome), a diagnosis is performed based on EIT images. In the EIT, the impedance distribution of the chest is continuously measured as a tomographic image by a chest impedance measurement.
There is a related-art technique in which, in the EIT, the lung region in a tomographic image is segmented into several ROIs (Regions of Interest), and the ratio of the value of an impedance integration of an ROI to that of the whole region is displayed in the form of a waveform or a numerical value (see U.S. Pat. No. 8,321,007).
The EIT images show the aerated state of the lungs. When aeration which is locally abnormally large is observed, there is a possibility that pulmonary alveoli are hyperextended. By contrast, when aeration which is locally abnormally small is observed, there is a possibility that pulmonary alveoli are collapsed. In treatment of ARDS or the like, it is important to know the hyperextended and collapsed states. However, the ratio of the value of an impedance integration of an ROI to that of the whole region which is obtained in the manner disclosed in U.S. Pat. No. 8,321,007 is a parameter from which the hyperextended and collapsed states are hardly known. Therefore, it is requested to obtain a parameter from which the hyperextended and collapsed states can be adequately known.